specifics on compression testing, P0301

[lanxer57]

No problem with the spark plug wires than? What else could cause these codes? Should I reset and see if these codes come back? (Because I can not drive it very much)

[billr]

I saw no problem with the routing, but have you checked the plug wires for resistance and shorts? Neither is likely to cause that P0340, however.

Yes, reset the code and see if it comes back, and how soon.

That entire CMP sensing system consists of the plugs, plug wires, ICM/coil module, PCM, and wiring from the ICM to PCM (including connectors). The plugs are new and gapped at about .040", correct? Swap the #1-4 coil with the #2-3 coil, see if that prevents the P0340. Next, check the ICM-PCM wiring for any obvious physical damage, including unplugging every connector in the circuit to inspect for corrosion or damage, and to "wipe" the connector contacts to clean off any minute corrosion that may not be visible. Check for corrosion where the ICM mounts to the engine.

Still no joy? Putting in a known-good ICM is probably the next step. This can be kind of tricky, though, since an ICM from a FLAPS or on-line vendor cannot be assumed to be "known-good"...

[lanxer57]

I blocked the EGR valve wit 2 pieces of a soup can smashed together. I did not feel a leak, and dad did not smell one. these were rough circles about the size of a quarter. None of the codes went away while idling. (P0172, P0733, and P0340) I will try resetting the computer tomorrow to see how long they take to come back. STFT was about 20%, and LTFT was about -14% with the EGR blocked this seems to be an improvement over the last readings I took. I checked the oxygen sensor readings again, and S1 was oscillating between 0.35-0.8 volts while S2 was oscillating between 0.1-0.45 volts, later 0.1-0.65 volts. Would a blocked EGR cause emission test failure itself? It sounds like something that would do that...

[billr]

Yes, I would expect the blocked EGR to cause a fail in two ways: it will probably increase the tail-pipe NOX above limits and it will probably set some more EGR-related codes. Let's see what codes you get after a reset.

I think you are going to have to check the injectors for leakage.

[lanxer57]

I can not test drive it again until the next time dad takes me to a junkyard. brake fluid is slowly seeping out of the passenger side rear drum brake wheel cylinder, and dad knows about it, so he will not let it leave the driveway. Are the wheel cylinders the same across all s series with drum brakes of all years? Are they different on DOCH models? Should I convert it to disk brakes if I can find them? (I live near mountains, and drive automatic trans)

In other news, P0340 came back while idling with EGR blocked.

This thread seems to be getting a bit off topic, Is it possible to rename a thread?

[lanxer57]

I switched the ignition coils among other things and reset the computer. none of the codes have come back after 30 minutes of idling. STFT was -30% and Ltft was 18% before it reached operating temperature. STFT later changed to -18%.
How accurate id the intake temperature sensor supposed to be compared to outside weather? 46F read as 72F when warming up and later as 122F. Is the RPM supposed to drop when the fan or headlights turn on? Just something I noticed.

[lanxer57]

P0340 came back again almost immediately as soon as I started the engine today. Could the blocked EGR have something to do with that? I only saw that code after I blocked it.

I also noticed something else: When the gas pedal is pressed or let go, the oxygen sensor voltage increases to 0.8V before tapering off after a few seconds and returning to oscillating. STFT also goes to 0%, when the throttle position changes, before tapering off in the same way back to -30%. The TPS works, there is nothing wrong with it. Does this mean anything?

[billr]

Blocking the EGR passages should set some codes, but I would not expect P0340 to be one of them. Put the EGR back to stock and see if the P0340 goes away. Then block/unblock it again a few more times, to see if that is a repeatable symptom.

Can you summarize what effect, if any, blocking the EGR has made on fuel trims? That was the main reason for suggesting blocking the EGR, to see how it affected trims.

You are using live-data to check the TPS? Does the live-data show injector pulse duration?

[lanxer57]

I have used live data to check the TPS, it works smoothly as the pedal is pressed. The cheap scanner that I have does not show duration if fuel injector pulse. With the EGR blocked, the fuel trim seems to have gotten closer to 0, which I believe is supposed to be normal, but I have never seen it reach 0 at idle. Codes usually seem appear when the vehicle is moving, but it can not move until the brakes are fixed, as the right rear wheel cylinder has developed a small leak. I am considering converting to rear disks if I can find them, because I live near the mountains.

[billr]

My opinion? Do not bother with the conversion to rear discs.

[lanxer57]

Will drums be okay even when I am driving down a mountain? There are lots of mountains about 20 miles west of where I live. Big ones, with lots of hills and corners. I am not a very good driver, and would like to keep major accidents to a minimum. I should also figure out if a SOCH with an automatic can even get up those inclines...

[billr]

Hills don't matter much, you should be down-shifting to use engine braking. It is more important how you drive. If you try for a smooth driving style, so as to maximize fuel economy, ride comfort, and safety; then braking is "light duty" even on hills. If a full-performance stop is needed for some emergency situation, then drums will handle that (one essential stop) every bit as good as discs. However, repeated heavy use of brakes, like in road-racing, will tend to overheat drums so that they fade and decrease in performance. Are you going racing with this beast? If so, I guess it will only be down-hill racing, since you already know it is under-powered for going uphill.

You need to get this back in a drivable condition, so you can pursue the engine issues. A wheel cylinder is only about $10, little loss if you later feel the urge to brag that you have rear discs and want to convert.

[lanxer57]

I was thinking I would get wheel cylinders and shoes even if I do manage to find a saturn with disks, just in case such a conversion failed. In my little experience, redundancy is never a bad thing...

[lanxer57]

After unblocking the EGR, I started it, and P0340 was gone and it did not come back as it was idling in the driveway. It was still running rich, STFT -30%, LTFT -17%. No codes appeared in the 30 minutes it was idling. I can not go to the junkyard this weekend, because moms exhaust is leaking again, and being a usable car, it gets priority. maybe next weekend, depending in dads mood.

[lanxer57]

I blocked the EGR again, and P0340 did not come back, so I do not know what caused that but I just hope it stays fixed. I am going to unblock the EGR again, because I am trying to pass an emissions test. I will not be able to visit the junkyard this weekend, because dad is tired of seeing error codes on moms 2010 traverse, and we will be trying to fix that instead because it actually matters, unlike my S series paperweight. I might get to work on it again at some point.

[lanxer57]

I switched out the brakes, test drove it, and the SES light came back on with P0172, P0733, and P0340, should I try changing oxygen sensors next?

[billr]

Clear the codes and see if the same ones consistently come back. Do this at least five times, making no changes. We need to have some confidence those are the only true codes now.

As to chasing them, I would go after the P0340 first, as it should be the easiest to solve. That has been discussed before; it has to be the ICM (includes coils), wiring, or plugs, plug wires, or ECM. Which of those parts have you checked now, and how?

Again, don't do anything until you clear codes and get them to repeat consistently.

[lanxer57]

I tried switching the coil towers, inspecting, and cleaning everything including spark plugs and wires, coil towers, and any connectors. I think I should bring a gas can because the gauge reads empty. I filled it halfway a few months ago. no point in checking oil level on our steep driveway.

[lanxer57]

P0340 has disappeared again. P0172 came back after 30 seconds of driving. P0733 came back a few seconds later and I actually felt it slip this time going maintaining a speed of 25MPH.

[lanxer57]

P0172 is gone. it is no longer running rich. I replaced bad fuel injectors with more bad fuel injectors. I just put some more in, and it runs better. I also messed with the oxygen sensor and need to replace it. I will start a new thread for my transmission problems.